Preheat the oven to 180°C.
Mix flour, polenta, baking powder, lemon zest, and cayenne pepper in a bowl.
Slowly stir in water until a thick batter forms, then add lemon juice and crushed garlic.
Heat half the oil in an ovenproof pan and fry the batter for 5 minutes per side.
Drizzle remaining oil over cornbread and bake for 5 minutes until golden.
Soften onion, celery, and garlic in a frying pan for 5 minutes.
Stir in the spices and herbs and cook for 2 minutes.
Add tomatoes and stock, bring to a boil, then simmer for 8 minutes to thicken.
Stir in both bean varieties and heat through for 4 minutes.
Cut cornbread into six pieces and serve topped with the bean mixture.